In a large bowl, toss pecans, cracker crumbs, brown sugar, and salt with a rubber spatula until combined.
Add cream and syrup and fold with spatula until mixture starts to clump and stick together. (This might take a few minutes, but keep mixing; it will work.)
Scoop rounded tablespoons of pecan mixture (about 20 g. each) and, with clean hands, form into a ball. Arrange balls on a parchment-lined baking sheet.
Freeze balls on sheet until firm to the touch and no longer sticky, about 30 minutes.
In a medium microwave-safe bowl, microwave chocolate and oil in 30-second increments, stirring between each, until melted and smooth, about 1 minute total.
Working one at a time, dip balls into chocolate, spooning chocolate over until coated. Using a fork, lift out balls, gently shake off any excess chocolate, and return to baking sheet. Top with more pecans.
Refrigerate truffles until chocolate is set, about 1 hour.
